High resolution data acquisition

What is data acquisition?

Many instrument applications require monitoring of analog signals, therefore they need a way to acquire and process data. Data acquisition involves sampling analog signals from various sensors, and converting these electrical signals into digital values, that can be displayed, analyzed, manipulated, and stored by a computer. Data acquisition is performed by analog to digital (A/D or ATD) converters.

The resolution of an ATD converter is specified in bits. For example, an 8-bit ATD converts an analog signal into one of 28 or 256 discrete digital numbers, while a 10-bit ATD converts an analog signal into one of 210 or 1024 discrete digital numbers.

The converter measures the input voltage with a specified resolution. The resolution is the granularity with which the measurement is performed. It can be specified as a number of bits or as a voltage increment. For example, an A/D converter with only 1 bit of resolution and a 5 Volt input range would classify all voltages from 0 to just under 2.5 Volts as the digital value 0, and voltages from 2.5 Volts to 5 Volts as the digital value 1. This converter would have a resolution equal to 1 bit, corresponding to 2.5 Volts per count. An A/D converter measures the input voltage with a specified accuracy. The accuracy tells how close the measured value is to the actual voltage. A typical 10 bit ATD converter is accurate to within plus or minus one least significant bit, equivalent to plus or minus 1/1024 of the input range.

Mosaic embedded controllers host high resolution analog to digital converters to address a wide variety of instrumentation and control applications. The controllers based on Motorola 68HC11 processor (such as the QCard and QScreen) include an 8-channel 8-bit analog to digital (A/D) converter that is built into the 68HC11 processor chip. The PDQ Board based on Freescale HCS12 processor hosts 16 channels of 10-bit analog to digital conversion. There are two A/D converter systems on the HCS12 processor, and each converter is controlled and configured by pre-coded driver routines in the operating system.

Need to expand your data acquisition system?

For applications that require versatile high resolution measurements, we offer tiny but powerful expansion modules which you can mix and match to build your custom off-the-shelf data acquisition system. Our controllers can host up to 8 expansion modules called Wildcards to boost data acquisition and interface to different sensors and actuators.

The DA-24/7 Wildcard

The Data Acquisition Wildcard gives you the ability to amplify and sample low level signals at various conversion rates directly from transducers using a sigma-delta technique. Its state-of-the-art analog-to-digital converter provides 24 bits of resolution with no missing codes performance. The 24/7 Data Acquisition Wildcard performs all signal conditioning and conversion for a system of up to seven input channels that are configurable in 10 different ways. This Wildcard also provides three general purpose digital inputs.

Mounted on any of Mosaic's single board computers, it provides a high performance analog front-end, offering exceptional resolution, stability, and noise rejection. Amplifier gain, low-pass filter corner frequency, and sampling rate are all software programmable using simple commands. Conversion rate is programmable from 4.8 Hz to 1010 Hz. Other features under software control include self-calibration, system calibration, input gain, filter cutoff, channel selection, signal polarity, and bipolar or unipolar input ranges.

The Signal Conditioning Wildcard is used with the Analog I/O Wildcard to increase its input and output voltage range and to add 4-20 ma current input and output capability. A stack of Analog I/O and Signal Conditioning Wildcards offers four channels of 4-20 mA inputs and four channels of 4-20 mA outputs with 16-bit resolution. In addition, it provides four channels each of 0-10V inputs and outputs. The low-cost stackable solution works exceptionally well in space-constrained embedded or portable applications, offering convenient interfaces to analog sensors and actuators.